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Re: [Phys-l] Step down transformer trouble



Try an ammeter on the input and output. A transformer is just two coils of wire. The only way those could fail is if they took too much power and melted. I'm surprised that you're not filling the room with dense black smoke. (Usually a sign that dinner is ready... or was about 20 minutes ago.)

Paul

On Jul 6, 2011, at 2:31 PM, Bernard Cleyet wrote:


On 2011, Jul 06, , at 03:37, Paul Lulai wrote:


I brought my multimeter in to school during out circuits unit. I can't check much right now.
The doorbell remains off. House power appears fine (all branches connected to the same line are behaving normally). That makes me think you're probably right with the secondary coil failure.
In terms of wiring: the transformer has 3 wires coming out if it. One green for ground, and two black. Two black wires is odd,

No is std. w/ xformers for domestic primary -- colour coding only when it makes a diif., e.g. the green gnd.


Still not know if it's the primary or secondary that fails -- since in a few min. and not while ringing, I suspect it's the primary and connected to 220V ??? Not sensible if connected to white and black instead of two blacks or other colour. Save the dead xformers for students to disassemble and use the wire -- these are usually not potted.

bc never found a failed bell xformer and seen many in his 60 + years of tinkering. The are designed for continuous use and used very intermittently!


but makes some sense in this application. One black wire is connected to a house black (hot). The other transformer black lead is connected to the house white (neutral) wire.

Paul Lulai
Physics Teacher
St Anthony Village Senior High
3303 33rd Ave
St Anthony Village MN 55418

(w) 612-706-1146




----- Reply message -----
From: "chuck britton" <cvbritton@mac.com>
Date: Wed, Jul 6, 2011 10:55 am
Subject: [Phys-l] Step down transformer trouble
To: "Forum for Physics Educators" <phys-l@carnot.physics.buffalo.edu>

What's the failure mode? (open secondary would be my guess)?

I don't follow the sentence on 'gounding'.


At 5:58 AM -0400 7/6/11, Paul Lulai wrote:
Hi.
We can't keep our doorbell stepdown transformer working. I thought
i would check this group for thoughts.
The transformer drops to 16v. That matches the input for our doorbell.

The transformer is connected to ground and both the black and white
house wires (as directed on installation instructions).

It is installed onto a standard junction box with (which has a cfl attached).
I've changed transformers multiple times. I checked the doorbell.
I found no problem, but thought a $20 change of bells might so it,
so I changed it anyway (after the 2nd transformer).
Any thoughts?
_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
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_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l


_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l